The effect of permethrin impregnated sisal curtains on vector densities and malaria incidence: a pilot study

ABSTRACT

Malaria is a major public health problem in the tropics and sub-tropics and has been shown to be a major cause of days of healthy life lost. Impregnation of bednets and curtains has been reported to reduce vector inoculation rates and malaria incidence. We conducted a qausi-exiperimental pilot study for three months in western Kenya on 20 houses with 54 children. 10 houses in the control area received either no sisal curtains or unimpregnated curtains while 10 others in the experimental site received impregnated curtains but at different concentration levels viz0.5 g/m2 and 1.0 g/m2). Vector densities and man biting rates were monitored once every two weeks using the spray sheet collection and the human bait catches. Bioassays using the standard WHO cone-method were done fortnightly. Malaria morbidity was monitored among the 54 children (22 in control and 32 in experimental) fortnightly by taking blood smears and temperature. In houses with impregnated curtains at 0.5 g/m2 vector densities were reduced by 97.7 while in the houses with 1.0 g/m2 the density reduction was 98.7. A 50 reduction was also observed in houses with unimpregnated curtains. On average man biting rates in houses with no curtains were 6.4 bites per man per night. In the houses with curtains the average bites per man per night were 1.7 (unimpregnated); 0.7 (0.5 g/m2curtains) and 0.4 (1.0 g/m2curtains). All mosquitoes exposed toimpregnated curtains (at both concentration levels) died; up to the fourth month;aftre which therewas decline in residual effect. There was no significant difference in malaria incidence at the two sites. We conclude that covering for eaves and windows with permethrin impregnated sisal curtains can reduce mosquito densities in the houses as well as the number of mosquito bites to individuals sleeping in those houses